How to get contact cleaner inside the input switches of a Hafler DH 101?

62vauxhall

62vauxhall

Addicted Member
Was hoping someone with past experience can answer this. I have a Hafler DH101 preamp that has dirty contacts in at least the phono input switches. There does not seem to any opening large enough to squirt contact cleaner into. At times, I have successfully used a hypodermic syringe to get cleaner through very small openings but there don't seem to be any at all on these switches. I am contemplating drilling a hole into the plastic case using only hand pressure but before trying that, I thought I'd ask if anyone knows a less invasive, less drastic method.
 

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If you spray Deoxit5 in the terminal side it should migrate to where it's needed thru whatever crevices it finds. These switches are notorious for developing intermittent contact interface.

Sent from my SM-N900V using Tapatalk
 
62,

Have you tried going in through the front of the switch where the button actuator goes into the switch body?

I have a Hafler DH-110 and that worked for me on some very dirty switches.

YMMV.

-L_B
 
The white plastic plate will come off if you pry it up over the terminals after you unsolder all the wires. Highly not recommended, don't do it, etc. But that's how they're put together. If you can't get in from the front as mentioned above, you might carefully pry up the white cap at the very back (if they're not actually open back there) and squirt it in there.

Millions of those switches in piano-sized recording consoles from the 80s-onward. They do pretty well with continuous use, but they do need their exercise...

Chip
 
Chip Chester said:
The white plastic plate will come off if you pry it up over the terminals after you unsolder all the wires. Highly not recommended, don't do it, etc. But that's how they're put together. If you can't get in from the front as mentioned above, you might carefully pry up the white cap at the very back (if they're not actually open back there) and squirt it in there.

Millions of those switches in piano-sized recording consoles from the 80s-onward. They do pretty well with continuous use, but they do need their exercise...

Chip
Click to expand...

It sounds like you may have done this and those white plastic tops are pressure fit and not glued?

I tried dripping deoxit onto the terminals hoping some would seep in and used a syringe to "inject" some inside through the front, exercising the switches afterward, but without success. I guess dissection is the next procedure.
 
There are different options for those switches from the mfg. Sometimes they are "sealed" for environmental or manufacturing reasons. If not, they are almost friction-fit over the terminals. But also, the terminals are friction fit. So it is possible to disassemble the whole thing, which would be aggravating. Best to sneak in if you can.

Chip
 
In the days before Dexoit became heavily promoted.
It was the usual drill to Pour Iso Alcohol through sketchy switches/pots.
Even a couple of ounces :-) ..
The black residues that often came out were dramatic.
Easy to do?? and Iso dries up very Quickly.
Iso alcohol is both inexpensive and readily available.
 
I have not tried this myself so this is not an endorsement. Simply bringing it to your attention for discussion and possibly as an option. Maybe someone here has done this and can shed some light.

In this youtube video a rebuilder of a Kenwood KA-8100 used a punch, heated with a torch, to melt a small hole in a switch. Skip forward to 14:12 in the video.

Also, if you do decide to drill, I have read somewhere that a bit of vaseline in the bit can help prevent chips from falling into the switch. Again, I have not tried this but it seems relevant to the discussion.
 
Do not pry the tops off. Bend the tip of the straw 90 degrees so you can spray directly on the seams. Spraying from the front is doable if you can get past the push button. Sometimes the only way is the "flush" method but that is costly with deoxit. I use MG Chemicals residue free for this reason.
 
roger2 said:
I have not tried this myself so this is not an endorsement. Simply bringing it to your attention for discussion and possibly as an option. Maybe someone here has done this and can shed some light.

In this youtube video a rebuilder of a Kenwood KA-8100 used a punch, heated with a torch, to melt a small hole in a switch. Skip forward to 14:12 in the video.

Also, if you do decide to drill, I have read somewhere that a bit of vaseline in the bit can help prevent chips from falling into the switch. Again, I have not tried this but it seems relevant to the discussion.
Click to expand...

I have not run across a switch that could not be cleaned with the "flush" method. IMO, punching a hole is a very bad idea.
 
SoCal Sam said:
I have not run across a switch that could not be cleaned with the "flush" method. IMO, punching a hole is a very bad idea.
Click to expand...

I agree. Punching sounds violent.

Melting a hole into plastic, using a heated tip of a metal tool, may be a viable alternative to drilling. The OP is considering drilling. Using a very hot, very thin (sized to fit the deoxit straw) piece of metal with a pointed tip, it may be possible to create a hole in plastic using less force that would be required by drilling, also without concern for where the shavings would fall because there would be no shavings. It seems to me there would also be less chance of an accidental slip of the hand resulting in the tool going too far into the switch, and possibly causing damage, because less pressure would be required melting a small hole vs drilling one. This is all speculation of course, but seems very plausible. The linked video does not show the process, only the result which appears clean and neat. I wonder if anyone on AK has tried this approach?

Unless I was certain how things were laid out inside I would be afraid to make a hole using either method. I am not suggesting that anyone should blindly put holes into switches. The switches in the link I posted have a translucent cover so in that case it was possible to locate a safe place to make the hole.

For switches with no openings there are no perfect solutions. IMHO spraying contact cleaner in through the front, depending on how a switch is constructed, could have a high probability of washing away lubricants intended to maintain smooth action of the mechanical parts.
 
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Deoxit is so expensive that it seems folks are reluctant to flush the switch. It works, IME.

Yeah, punching and or drilling a hole risks far greater problems. The process will produce debris that could foul the contacts which would be an even worse problem. Oh well, its your gear.
 
Reading Bare's post about the past practice of using ISA in quantity to flush switches got me to think about removing the entire switch block, immersing it an ISA "bath" for a couple of days and repeatedly "exercising" during the process. ISA is relatively cheap and a not too wasteful plastic container is easy to come by. Other than dealing with unsoldering and re-soldering the wires, any cons to this idea?
 
62vauxhall said:
Reading Bare's post about the past practice of using ISA in quantity to flush switches got me to think about removing the entire switch block, immersing it an ISA "bath" for a couple of days and repeatedly "exercising" during the process. ISA is relatively cheap and a not too wasteful plastic container is easy to come by. Other than dealing with unsoldering and re-soldering the wires, any cons to this idea?
Click to expand...

Ok, here is my opinion. Meaning no disrespect to those who disagree.

Unless you have reason to believe that these switches are the causing some issues that you are experiencing, I would leave them alone. As access is problematic, I would not clean them just to be cleaning. But if the switches are causing problems and something really needs to be done...

Submerging in alcohol is the cheapest and easiest approach. That is a red flag to me, ymmv.

I have opened up a few metal switches (not plastic like yours, but I have no reason to believe they would be different inside). In some of the switches I have found a dark, thick substance right on the contact areas that looks like some type of grease. I believe it is possible that the black looking stuff that one might see as a result of soaking in alcohol could be this grease dissolved in the alcohol. In addition to that, there is usually some grease on the purely mechanical, moveable parts. Large amounts of alcohol is probably not going to do anything good for these lubricants, worst case it might dissolve them completely changing the feel (and perhaps lifespan) of the switches. I question the effectiveness of alcohol in actually removing corrosion on the contacts, especially in comparison to Deoxit which is engineered specifically for this purpose and is generally acknowledged as an excellent product.


But to be fair, alternative approaches would require extreme care and exceptional skill. If I was doing this, my first thought would be to disassemble at least one of the switches. But that would be risky. I have successfully opened and closed a few metal, never plastic, switches. Once inside a switch it is possible to do a much more thorough cleaning, directly on the contact areas, and you can use D100L which is pure cleaner with no solvents, so lubricants on moving parts can be left undisturbed.

If I did not feel that I could disassemble/reassemble the switches safely, I might try putting a deoxit straw sized hole in the far end of the switch, opposite to the push-button end. Then spray D5. If someone wanted to seal the hole afterwards I think that could be done (carefully) with some JB Weld.

Good luck and please keep us posted on whatever you decide to do. I have some similar looking switches in my current project (Sherwood S-602CP).

EDIT: If you do decide to make a hole by any method, be careful not to allow the tool to enter into the case of the switch any further than necessary. If it is possible to open one switch then you would know how deep you could go safely. If not, then caution and a steady hand. Please don't attempt if you don't feel confident about doing it.
 
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I hope I'm not tempting fate by saying this but reluctantly and with hat in hand, I have to confess that the input source selector switches seem to be OK. My problem seems to be the mechanical speaker binding post connection in the completely rebuilt power amp I've been using.

The DH101 is the second preamp I've installed in my system and the second one to exhibit one channel cutting out. Touching the first preamp's balance control caused the channel to come and go so I swapped it out for the Hafler which I've been suspicious of for as long as I've had it. Only in it's case, it was operating the phono switch than affected the channel. I could buy that both preamps were problematic for different reasons and since the new balance control I acquired for that first one was not a completely correct fit, I focused on the DH101.

Last night, I installed a third preamp and experienced exactly the same problem only no matter what control I touched, the dead channel remained dead. It seemed unlikely to me that 3 different preamps would exhibit the same problem, so duh, it must be something else. I unhooked the in use power amp, swapped it and guess what, both channels working with the Hafler.

Because that first power amp was a total re-build and worked perfectly for the last few months, I did not anticipate that it was the cause but while disconnecting speaker bananas from binding posts, I noticed that finger pressure brought the channel back. Part of the re-build was installation of a speaker protection relay board that uses a threaded portion of the binding posts as anchor points for the circuit board as well as being how the amplifier's output connect to the them. Haven't popped the hood yet but I'm fairly certain I have an intermittent connection in there.

I wish to thank all those who contributed suggestions on how to clean those switches and will definitely file that away for future reference as valuable information.

Over the last few years, I've come to the conclusion that vintage audio stuff is as persnickety to keep going as vintage motorcycles.
 
ISA has water which is corrosive. Instead of expensive deoxit, use MG Chemicals residue free cleaner available at Fry's. Can size is double and the price is half. It works just as well and you can flush without flushing your money away.
 
62vauxhall said:
Over the last few years, I've come to the conclusion that vintage audio stuff is as persnickety to keep going as vintage motorcycles.
Click to expand...

Part of the fun of this hobby,right?

I was sure I had a problem with my power amp a little while ago, but after a lot of time spent chasing down the problem, discovered it was dirty switches on my preamp. Anything is possible...
 
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